1. Field of the Invention
The present invention relates to batteries used for electric tools, and in particular to batteries used as power sources of electric tools.
2. Description of the Related Art
A known battery used for an electric tool is disclosed, for example, in Japanese Laid-Open Patent Publication No. 2010 93953. The battery disclosed in this publication can operate in an active mode during use of the battery, i.e., when a battery charger is connected to the battery or when the electric tool is connected to the battery and a tool main switch is turned on. In the active mode, a power is supplied to a peripheral circuit under the control of a microcomputer for performing a charge control or a discharge control of the battery.
The battery operates in a sleep mode during the non-use of the battery. In the sleep mode, the microcomputer stops the supply of power to the peripheral circuit. Therefore, it is possible to save the power consumption of the battery during non-use of the battery.
However, in the sleep mode, a part of the function of the microcomputer is stopped or the microcomputer stops the operation of the peripheral circuit. Therefore, it is not possible to detect the condition of the battery, such as a temperature, a voltage and a discharge current of the battery. For this reason, historical data of the battery condition cannot be obtained in the sleep mode.
The period of life of the battery may be largely affected by the environmental condition, such as an ambient temperature of the place where the battery is positioned. However, because the historical data cannot be obtained during the sleep mode, it is difficult to recognize as to what environmental condition the battery has been placed during the sleep mode.
Therefore, there has been a need for a technique that enables to obtain data of a battery condition even during non-use of the battery.